Challenges in Optical Wireless Communications

Indoor

FSO

InterSymbol Interference

(ISI)

Causes

Effects

Solutions

Multipath propagation

Quality of the Transmission

Multipath Dispersion

Equalization ,FEC

In/FSO

Spread Spectrum Techniques

In/FSO

Multiple-Subcarrier Modulation

(MSM).

In/FSO

Reduce Data Rates

OFDM

In/FSO

Multi-Beam Transmitter

Indoor

FOV controlling

Indoor

Safety

Laser radiation

Damage to eyes

and skin

Power Efficient Modulation

PPM,DPIM, etc.

In/FSO

Use LED

Indoor

Noise

Dark Current Noise

Limit performance of communication system

Optical and Electrical filtering

In/FSO

Shot Noise

BER deterioration

Pre-Amplification

In/FSO

Background Noise

FEC

In/FSO

Thermal Noise

Low Noise Amplifier

In/FSO

Relative Intensity Noise

In/FSO

Excess Noise

APD-amplification process

In/FSO

ASE

In/FSO

Turbulence

Random reflection index variation

Phase and Intensity fluctuations (Scintillation)

Choosing different Coding, e.g. LDPC,FEC

FSO

Image dancing

MIMO

FSO

Diversity reception

(Temporal and Spatial)

FSO

Adaptive Optics

FSO

Reflection Index

Different Materials

Reflected Power

Indoor

Blocking

Furniture

Moving objects

Link Loss

Diffuse link

Indoor

Cellular System, MIMO

In/FSO

Walls

Multi-beam

In/FSO

Birds

Hybrid FOS/RF

FSO

Bit Error

Noise

Bit Error Rate

FEC

In/FSO

Multipath

Block code

In/FSO

Convolutional Code

In/FSO

Turbo Code

In/FSO

Weather

Effects

Fog, Rain, Gases, Smoke, Aerosols

Attenuations

Scattering

Link Loss

Hybrid FSO/RF

FSO